Emulator:-
In computing, an emulator is hardware or software that enables one computer system (called the host) to behave like another computer system (called the guest). An emulator typically enables the host system to run software or use peripheral devices designed for the guest system.
Performance Emulators are really slow. Emulating the actual hardware usually makes the software run slower than it would natively.
Example:- Google's Android SDK
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Simulator:-
A mobile simulator is a software application for a personal computer which creates a virtual machine version of a mobile device, such as a mobile phone, iPhone, other smartphone, or calculator, on the computer. This may sometimes also be termed an emulator.
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Faster than emulators
Example :-Apple's iOS Simulator